Intel allows BIOS or the OS to enable or disable some CPU fueatures viaIA32_MISC_ENABLE. I have machines that don't enable fast strings ormonitor/mwait in BIOS, so do it on bootup instead.

The Intel SDM volume 3, appendix B.1 says that the OS should not touchthe monitor enable bit if SSE3 is not present, which presumably meansthat the OS may touch that bit if SSE3 is present. In any case, thesepatches seem to work.